This invention relates to a method and a device for feeding rod-like articles, particularly cigarettes, by means of trays, into the feed hopper of handling machines, particularly cigarette-packing machines.
By the term "trays" are meant herein parallelopiped containers, open at the top and at one side face, in which said rod-like articles or cigarettes are orderly arranged in superposed layers.
Feeding devices of the specified type are known in which the full tray, after the automatic introduction thereof in a casing or frame, which closes the open sides thereof, is overturned on the hopper which gradually receives the contents thereof by opening a suitable bottom wall of the casing.
The command to replace an emptied tray with a full one is issued, usually, by a photocell-sight device detecting the level of the articles in the hopper.
Between the moment at which the replacement command is issued and the moment at which the bottom wall of said casing is opened, a period of time elapses during which the level of the articles in the hopper falls down.
As a consequence, upon the opening of the bottom wall of the casing, the articles issuing from the tray will experience a sudden drop the extent of which increases with the speed of the packing machine, by maintaining the same period of time to replace the tray.
Such a drop, obviously, creates operational disturbances, and in order to avoid or minimize them within satisfactory limits, devices have been proposed to feed rod-like articles in trays to a hopper in which a rotary turnover device comprises a pair of frames or casings each of which can receive a full tray, whereby while the tray of one casing is discharging its batch of articles into the hopper, suitable substitution means remove an emptied tray from the other casing and arrange a full tray therein, so that as soon as the tray on the hopper has been emptied, said turnover device will rotate so as to turn a full tray over said hopper.
Still for the purpose of minimizing the time for said substitution, tray-supplying devices have been devised wherein a full tray is previously brought into a stand-by position in proximity of the hopper.
Other tray-supplying devices have been proposed wherein, by means of retractable walls, for example of winding or telescoping type, supplemental storing volumes are generated at a due time, momentarily extending the side walls of the tray, whereby an emptied tray can be moved away beforehand and a new full tray can be brought into the discharge position.
The main object of this invention is to provide a method for feeding cigarettes or other rod-like articles by means of trays to the feed hopper of a handling machine, and particularly a packing machine, so as to avoid practically any drop of the cigarettes from the tray to the hopper and the resulting consequences, yet affording a sufficient period of time to replace an emptied tray.
The method according to the invention is substantially characterized by the fact that two trays in discharge position are placed over the inlet opening, and are aligned to each other in the direction of the larger dimension of the hopper inlet opening and the descent of the cigarettes is permitted alternately only from one of said trays until it is emptied, while the other emptied tray is replaced with a stand-by full tray.
Substantially, according to the method of the invention, a hopper whose inlet opening has a major dimension which is twice that of one tray is fed by a pair of trays which are aligned in the direction of their length and are both in the discharge position, while the discharge of cigarettes into the hopper below one of the trays is prevented, and the means preventing the discharge are switched over to the other tray whenever the functions of the trays are to be switched over, i.e. upon each changeover from the stand-by step to the discharge step, and vice versa.
More particularly, the discharge of cigarettes into the hopper portion being fed in discontinued as soon as the tray which is discharged has been emptied, whereby the level of the cigarettes in this hopper portion is kept unchanged. This level, upon the replacement of an emptied tray with a full one, will be just below the cigarettes resting on the bottom of the casing that houses said new tray. When a tray in the discharge step is being emptied, the descent of the cigarettes into the hopper portion below the stand-by tray is prevented, so that the pre-established level of cigarettes in this hopper portion will not change. The descent of the cigarettes into the hopper portion below the stand-by tray will be permitted immediately after the depletion of the tray being discharged into the other hopper portion.